The deliberate injection of interference signals in an operating region of a wireless information service is a common technique to interrupt the flow of data to a user, and can often have drastic consequences. For example, when signals of a global positioning system (GPS) are interfered with, such as by signal jamming or data spoofing, a user may find him- or herself out of position. In a battlefield scenario, proper positioning with respect to that of the enemy and that of friendly forces is often critical, and failure to comply with planned trajectories can result in damage to equipment, injury to personnel and even loss of life. Accordingly, such deliberate interference is a common element of modern warfare and has been for many decades.
As used herein, jamming refers to the generation of electromagnetic radiation with the purpose of deliberately disrupting the successful transmission of data on a communication link. Spoofing, on the other hand, refers to the generation of electromagnetic radiation that mimics a communication link with the purpose of conveying false information to a user. A simple jamming strategy for GPS is to place a jamming source at the receiver, where the GPS signal strength is around −150 dBm. A GPS jamming source needs a jammer-to-signal (J/S) ratio of at least +80 dB to jam an incoming GPS signal and introduce bit errors. By jamming a satellite's broadcast signal in the vicinity of the targeted receiver, a much smaller and less powerful jamming source is needed. Jammers exist that can be fitted into a hand-held device that can be placed essentially at will.
GPS spoofing has emerged as an ongoing threat in both military and civilian contexts. Portable GPS satellite simulators exist that can fit into the trunk of a car and are available as commercial of-the-shelf items. Again, the small size of this interference equipment affords its placement in a region at will and without the knowledge of targeted personnel. It becomes a challenge to detect the sudden appearance of jamming and spoofing efforts without deploying special equipment, which may hamper such detection in real time. In light of these challenges, the need has been felt for a technique to alert personnel, both at a local level and at a regional level, as to the presence of jamming and/or spoofing efforts.